Temperature responsive switch having free floating disc actuator



Jan. 4, 1966 J, BARZ 3,227,845

TEMPERATURE RESPONSIVE SWITCH HAVING FREE FLOATING DISC ACTUATOR Filed Aug. 1, 1962 IIIIH v I y 5 I 4 a a I 3* 2? 25L? INVENTOR flay/Z Z01 2 ATTORNEYS United States Patent 3,227,845 TEMPERATURE RESPONIVE SWITCH HAVING FREE FLOATING DEC ACTUATOR Joseph Bar-z, 2070 Washington Lane, Meadowbrook, Pa. Filed Aug. 1, 1962, Ser. No. 213,971 6 Claims. (61. 200-138) This invention relates to temperature responsive devices, and particularly to devices which will operate when predetermined temperature changes take place, or when predetermined temperatures are reached, to make or break circuits controlling the operation of equipment of various kinds.

Many thermal responsive switch-closing devices are available for controlling automatic equipment of all kinds. These devices have used several different basic thermal responsive means as their operators. They include mercury columns, vented air chambers using the rate of rise principle, closed air chambers, and the well-known bimetallic elements. These are all useful in particular fields.

The bimetallic element is one of the best-known and reliable of the switch closing operators. There are certain characteristics of the element, however, which have made it undesirable for certain uses. It is not fast acting under most circumstances. Usually considerable length is required to provide the necessary movement, which sometimes necessitates a bend to procure the needed length in a given space. Another characteristic of this element which accounts to some degree for its lack of speed and limits its field of use, is the loss of initial calibration, or rate of movement, under a predetermined temperature change, if the element is restrained at high temperatures for a long time. In other words, all metals will grow weaker under temperature increases and they may take a set if restrained at high temperature and not return to the original cold position. This calls for a free end in most installation, unless a snap action is desired. Snap action discs and similar arrangements, however, are quite slow in effective response to temperature changes.

The general object of the present invention is to provide bimetallic element switch control which is greatly improved over prior instruments.

A more specific object is the provision of thermal responsive instrument which utilizes a bimetallic element as the actuator which will respond very rapidly to temperature changes.

Another object is to provide a thermally responsive unit using a bimetallic element wherein the element is mounted for unrestrained movement to improve its operating efficiency and calibration retention.

A further object is to provide a device of this kind having the bimetallic unit suspended from the main body of the instrument in a thin-shelled metal chamber for quick heat transfer to the element, with the chamber having a low mass connection to the body to retard heat loss to the retaining body.

Still another object of the invention is to provide a temperature responsive unit with a bimetallic element wherein the element is free floating in its mounting and self aligning.

Yet a further object is the provision of a bimetallic element of improved design and an improved mount for the element.

Other objects of the invention will become apparent from the following description of one practical embodiment thereof, when taken in conjunction with the draw ings which accompany, and form part of, this specification.

In the drawings:

FIGURE 1 is a vertical section through a thermal responsive instrument embodying the principles of the Present invention;

FIGURE 2 is an elevational view of the back side of the instrument; and

FIGURE 3 is a section through the control element suspending chamber, and is taken on the line 33 of FIGURE 1.

In general, the invention is concerned with a temperature responsive instrument which uses a bimetallic element as the actuator, wherein the bimetallic element is of spider shape having a plurality of legs supported rockably and slidably in a seat, or seats, with the element having a diaphragm-like movement to actuate a switch.

Referring to the drawings in detail, there is shown a temperature responsive unit 1, having a body 2 and a control chamber 3 suspended from the body. The body carries a switch actuator which responds to temperature changes.

The body 2 is shown as being circular in shape, having a back 4 to permit flush mounting upon a wall, or ceiling, or other suitable surface, and a front 5 which is slightly crowned. The body has a cup-like cavity 6 opening to the back, with a bridge plate 7 providing a mounting member for the switch arms, and forming a closure for an inner sealed switch compartment 8. Plate 7 seats upon a circular shoulder 9 within the cavity 6 and epoxy resin, or other suitable material, is used to form a seal 10 around the rim of the plate. Holes 11 are provided at diametrically spaced points to accommodate screw, or bolts, for mounting the instrument on a desired surface. The entire body will be formed of an insulating material.

The bridge plate 7 is aper-tured at spaced diametric points to receive rivets 12 and 13, which secure switch arms 14 and 15 to the underside of the plate within the switch compartment 8. The two switch arms extend radially inwardly from the points of attachment to overlap one another in normally spaced relation beneath the plate center. The arms are resilient and biased away from one another. Contact plates 16 and 17 are held in place against the opposite side of the plate. These carry binding posts 18 and 19.

The bridge plate has an upstanding boss 20, centrally recessed, as at 21, and a threaded opening 22 centrally of the plate communicates with the recess. A calibrating screw 23 is screwed into the opening 22 for adjusting contact with switch arm 15. The screw can be moved in or out to set with precision the inoperative gap between the switch arms. After the device is calibrated, the screw position can be set and the recess sealed by epoxy.

The chamber 3 is formed of very thin sheet metal. It has inner and outer shell sections 24 and 25, having perimetral flanges 26 and 27 compression welded after assembly. The inner shell section has a central collar 28, which serves as a guide tube for a plastic switch plunger 29 and as a mounting post for the chamber. The collar passes through an aperture 30 in the body leading axially into the switch chamber. The inner end of the collar is flared to form a retaining flange 31 to hold the chamber to the body. Sealing material may be applied around the flange edge to complete the seal of the switch compartment and chamber.

Plunger 29 has its inner end in contact with the free end of switch arm 14 and its outer end seated upon a bimetallic operator element 32. The bimetallic element is in the form of a spider having a central body 33 and a plurality of radiating legs 34. The legs are spaced equiangularly around the body for balance. The outer ends of the legs are bent to form curved feet 35 which rest in an annular groove 36 formed in the outer shell section 25. The groove is curved in cross-section, and formed on a greater radius than the feet 35 of the bimetallic element so that the feet will be unrestrained for rocking and sliding movement in the groove. It will be obvious that the groove could be discontinuous with just a well for each foot of the element, but the continuous groove allows freedom of action of the spider element and permits the bimetallic unit to assume any circumferential orientation. As shown in FIGURE 1, the spider is recessed centrally, as at 37, to seat the plunger and center the assembly. The outer shell section has a matching central recess 38 to receive the offset center of the operator element.

The instrument as above described will have the switch compartment and communicating operator chamber hermetically sealed to keep out all moisture and dust and eliminate dangers from arcing. The switch gap can be adjusted with precision so that the instrument can be calibrated to operate at any predetermined temperature plus or minus one degree. The calibration will not be disturbed by the instrument being subjected to higher temperatures than that necessary to operate the switch, as the bimetallic element feet, three as shown, can rock and slide in the groove 36 so that the element remains unrestrained. Under normal operation, however, the center of the element will rise first in response to temperature rise to move the plunger and close the switch arms. Only when no further movement of the central section can take place will the feet begin to slide outwardly in the groove. Prior to this, rising or falling of the central body of the element will cause the element feet to rock in the groove.

In operation of the device the bimetallic element 32 will be substantially flat and in contact with the outer section 25 of the shell when the temperature of the air in the locality of the device is normal. Thus the plunger 29 will be held against the spider "by the spring switch arm 14, and the switch arms 14 and 15 will be out of engagement. When there is an exceptional temperature rise in the area of the device, the thin metal of the shell will heat quickly, heating the air Within the shell and the bimetallic element. This shell will cause the bimetallic element to are as shown in dotted lines in FIGURE 1, moving the plunger and causing switch arm 14 to make contact with switch arm 15. This will serve to actuate any alarm or sprinkler system to which the device is connected.

While in the above one practical embodiment of the invention has been disclosed, it will be understood that the particular structural details shown are merely by way of example, and the invention may take other forms within the scope of the appended claims.

What is claimed is:

1. A temperature responsive device comprising, a body and a control chamber suspended from the body, the body having a switch compartment therein and the chamber being in open communication with the compartment, normally open switch arms in the switch compartment, means extending from the control chamber to the switch compartment to close the switch arms, and a bimetallic element in the control chamber in contact with the switch closing means, the bimetallic element having a central body and legs radiating from the central body, the control chamber having a seat to receive each leg of the bimetallic element, and the control chamber being thin metal and suspended from the body by a restricted neck to minimize heat transfer to the body.

2. A temperature responsive device comprising, a body and a control chamber suspended from the body, the body having a switch compartment therein and the chamber being in open communication with the compartment, normally open switch arms in the switch compartment, means extending from the control chamber to the switch compartment to close the switch arms, and a bimetallic element in the control chamber in contact with the switch closing means, the bimetallic element having a central body and legs radiating from the central body, the control chamber having a seat to receive each leg of the bimetaL lic element, and the bimetallic element legs terminating in arcuate feet, and the seats in the control chamber being arcuate with a larger radius than the arcuate feet.

3. A temperature responsive device as claimed in claim 2 wherein, the seat in the chamber is a continuous groove.

4. A temperature responsive device comprising, a body and a thin metal control chamber suspended from the body by a restricted neck to space the control chamber from the body for full exposure to atmosphere and to minimize heat transfer to the body, the body having a switch compartment therein and the chamber being in open comunication with the compartment through the neck, normally open switch arms in the switch compartment, means extending from the control chamber through the neck to the switch compartment to close the switch arms, and a bimetallic element in the control chamber in contact with the switch closing means, the bimetallic element having a central body and legs radiating from the central body and terminating in feet, the control chamber having an arcuate seat to receive each leg of the bimetallic element with the arcuate seat being of larger radius than the arcuate feet in a direction radially of the bimetallic element, whereby each foot of the bimetallic element may rock and slide in the seat during the fiexure of the bimetallic element under temperature changes.

5. A temperature responsive device as claimed in claim 4 wherein, the seat in the chamber is a continuous annular groove.

6. A temperature responsive device as claimed in claim 5 wherein, the central body of the bimetallic element is centrally recessed to seat the switch closing means.

References Cited by the Examiner UNITED STATES PATENTS 1,809,304 6/1931 Matthews 200138 2,239,541 4/1941 Spencer 200138 2,333,291 11/1943 Brannon 200-138 2,368,193 1/1945 Boynton 200138 X 2,543,040 2/1951 Mertler 200138 2,752,454 6/1956 Kurtz 200-438 FOREIGN PATENTS 676,657 7/1952 Great Britain.

BERNARD A. GILHEANY, Primary Examiner. 

1. A TEMPERATURE RESPONSIVE DEVICE COMPRISING, A BODY AND A CONTROL CHAMBER SUSPENDED FROM THE BODY, THE BODY HAVING A SWITCH COMPARTMENT THEREIN AND THE CHAMBER BEING IN OPEN COMMUNICATION WITH THE COMPARTMENT, NORMALLY OPEN SWITCH ARMS IN THE SWITCH COMPARTMENT, MEANS EXTENDING FROM THE CONTROL CHAMBER TO THE SWITCH COMPARTMENT TO CLOSE THE SWITCH ARMS, AND A BIMETALLIC ELEMENT IN THE CONTROL CHAMBER IN CONTACT WITH THE SWITCH CLOSING MEANS, THE BIMETALLIC ELEMENT HAVING A CENTRAL BODY AND LEGS RADIATING FROM THE CENTRAL BODY, THE CONTROL CHAMBER HAVING A SEAT TO RECEIVE EACH LEG OF THE BIMETALLIC ELEMENT, AND THE CONTROL CHAMBER BEING THIN METAL AND SUSPENDED FROM THE BODY BY A RESTRICTED NECK TO MINIMIZE HEAT TRANSFER TO THE BODY. 